1. Field of the Invention
The present invention relates to air ducts for automobile heating and venting, or air conditioning systems, and in particular to adjustable air outlet nozzles for such systems which are closable by means of a built-in clappet valve.
2. Description of the Prior Art
Heating and venting or air conditioning systems in automobiles are normally provided with several air outlets into the interior of the automobile, the air outlet ports being preferably equipped with an adjustable air nozzle whose setting controls the volume and direction of the air flowing into the interior of the vehicle.
A known adjustable air nozzle of this type consists essentially of a nozzle shell of spherically curved exterior contour received inside a matching lodgement of a connector housing, the nozzle shell engaging the lodgement through the intermediate of a surrounding sliding ring of textile material, preferably felt, so that the shell is universally pivotable inside the housing. This known nozzle, which is disclosed in U.S. Pat. No. 3,420,448, further includes a clappet valve arranged inside the nozzle shell, which valve is a so-called double-clappet valve, adjustable by means of a wing knob and bevel gear drive. The latter includes a driving gear on the longitudinal axis of the air nozzle and a driven gear attached to each of the two valve clappets, respectively, the latter being arranged to pivot in opposite directions on a common shaft.
This prior art device has the shortcoming that the felt ring on the outside of the nozzle shell often becomes prematurely worn as a result of frequent adjustments of the air nozzle, so that the friction between the nozzle shell and the connector housing diminishes to a point where it can no longer transmit the force which is exerted on the wing knob during adjustment of the double-clappet valve. The result of this situation is that an attempted adjustment rotation of the wing knob causes the nozzle shell to rotate inside its housing, rather than adjust the position of the nozzle valve. It then becomes necessary to use both hands, or other suitable implements, for the adjustment of the volume of air flowing through the nozzle.
An additional shortcoming of this prior art device is the fact that its valve is not suitable for a sensitive adjustment of the air flow, as even a small rotation of the adjustment mechanism results in a large change in the valve aperture, thus making it difficult to accurately adjust a desired air flow.